Plasma arc torches, also known as electric arc torches, are commonly used for cutting, marking, gouging, and welding metal workpieces by directing a high energy plasma stream consisting of ionized gas particles toward the workpiece. In a typical plasma arc torch, the gas to be ionized is supplied to a distal end of the torch and flows past an electrode before exiting through an orifice in the tip, or nozzle, of the plasma arc torch. The electrode has a relatively negative potential and operates as a cathode. Conversely, the torch tip constitutes a relatively positive potential and operates as an anode. Further, the electrode is in a spaced relationship with the tip, thereby creating a gap, at the distal end of the torch. In operation, a pilot arc is created in the gap between the electrode and the tip, which heats and subsequently ionizes the gas. Further, the ionized gas is blown out of the torch and appears as a plasma stream that extends distally off the tip. As the distal end of the torch is moved to a position close to the workpiece, the arc jumps or transfers from the torch tip to the workpiece because the impedance of the workpiece to ground is lower than the impedance of the torch tip to ground. Accordingly, the workpiece serves as the anode, and the plasma arc torch is operated in a “transferred arc” mode.
In automated plasma arc torch applications, the plasma arc torch operates at current levels between approximately 10 amps and 1,000 amps or more. At the higher current levels, the torch correspondingly operates at relatively high temperatures. Accordingly, torch components and consumable components must be properly cooled in order to prevent damage or malfunction and to increase the operating life and cutting accuracy of the plasma arc torch. To provide such cooling, high current plasma arc torches are generally water cooled, although additional cooling fluids may be employed, wherein coolant supply and return tubes are provided to cycle the flow of cooling fluid through the torch. Additionally, a variety of cooling and gas passageways are provided throughout various torch components for proper operation of the automated plasma arc torch.
These automated plasma arc torches are typically operated over a workpiece, or multiple workpieces, which are positioned and held onto a receiving table. The automated plasma arc torch processes one or more desired features or patterns from the workpieces on the table. After processing, a residual portion of the workpiece (sometimes referred to as a “skeleton”) that does not form a part of the specific geometrical patterns remains on the table and is subsequently discarded prior to another workpiece being positioned for processing.